Air quality in New York City has become among the most polluted of any city in the world thanks to smoke from over 100 wildfires in Canada enveloping the northeast of the U.S this week. According to the IQAir World Air Quality Index, New York City’s air quality was worse than any other city at 10 p.m. on Tuesday night and was still considered “very unhealthy” early Wednesday. City officials urged New Yorkers to remain indoors wherever possible and at-risk residents have been encouraged to wear masks. “If you are an older adult or have heart or breathing problems and need to be outside, wear a high-quality mask (e.g. N95 or KN95),” the office of Mayor Eric Adams said in a statement late Tuesday. Adams said precautions are being taken “out of an abundance of caution to protect New Yorkers’ health.” The smoke is expected to remain in the city for several days.